熔石英后表面坑点型划痕对光场调制的近场模拟

Simulation of field intensification induced by pit-shaped crack on fused silica rear-surface

建立了坑点型划痕的旋转抛物面模型,用三维时域有限差分方法研究了熔石英后表面坑点型划痕随深度、宽度、间距以及酸蚀量变化对波长λ=355 nm入射激光的调制.研究表明,这类划痕调制最强区位于相邻两坑点的连接区,且越靠近表面调制越强.当其宽深比为2.0—3.5、坑点间距约为坑点宽度的1/2时,可获得最大光场调制,最大光强增强因子(LIEF)为11.53;当坑点间距大于坑点宽度时,其调制大为减弱,相当于单坑的场调制.对宽为60δ(δ=λ/12),深和间距均为30δ的坑点型划痕进行刻蚀模拟,刻蚀过程中最大LIEF为11.0,当间距小于300 nm时,相邻坑点由于衍射形成场贯通.

Rotating paraboloid model is establishd,and three-dimensional finite-difference time-domain method is used to simulate pitshaped cracks on fused silica rear-surface.The light intensification with its depth,width,gap distance and etch value are investigated under 355 nm laser incident.Results show that the strongest modulation is located at the connection area between pit and pit,and the modulation become strong with approaching to the surface.The maximum light intensity enhancement factor（LIEF） is 11.53 when the breadth depth ratio ranges from 2.0 to 3.5 and gap distance close to 1/2 width.As gap distance greater than the width,the modulation reduces greatly,which is equal to a single pit.For 60δ-width,30δ-depth and 30δ-gap distance cracks,the maximum LIEF is 11.0 during the acid etching.As the gap distance is less than 300 nm,the diffraction of the light field makes the neighbor pits connective.